1. Field of the Invention
The present invention relates to a pump to be used as water pump or the like for cooling an engine of an automobile.
2. Description of the Related Art
As a conventional pump of this type, a pump shown in FIG. 13 is well known. The pump is constructed by comprising a housing 500 formed with a shaft bore 501, bearings 502, a shaft 503 rotatively supported by the inner peripheral portion of the shaft bore 101 through the bearings 502, wherein an impeller 505 to be inserted into a pump chamber 504 is connected to one end portion of the shaft 503. As the bearing 502, a rolling (roller) bearing has been used.
In recent years, however, there arise a great demand for forming the pump so as to have a light weight and a small size. In order to satisfy this demand, there have been made trials for lightening the weight of the pump by replacing materials for constituting the pump members such as housing 500 or the like by resin. However, due to existence of the rolling bearing, there is a limit for lightening the weight of the pump.
As a countermeasure for solving this problem and further lightening the weight of the pump, there has been made an investigation about using a sliding bearing in place of the rolling bearing. However, in case of the sliding bearing, a sliding surface thereof is liable to wear, so that there is posed a problem of durability of the pump being lowered.